Antioxidants for mineral oil lubricants and compositions containing the same



Patented June 13, 1950 ANTIOXIDANTS FOR RAL OIL LUBRI- CANTS AND COMPOSITIONS CONTAINING THE SAME Herschel G. Smith, Wallingford, and Troy L. Cantrell, Lansdowne, Pm, and John G. Peters, Audubon, N. J assignors to Gulf Oil Corporation, Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application December 21, 1948,

Serial No. 66,588

18 Claims. (Cl. 252-50) This invention relates to antioxidants for mineral oil lubricants and compositions containing the same, and more particularly, it relates to addition agents for mineral oil lubricants which inhibit the oxidative deterioration of said lubricants.

In the lubrication of internal combustion engines of all types, particularly when severe operating conditions are encountered, plain mineral lubricating oils often prove unsatisfactory in service because of the oxidative deterioration of the oil, with the attendant deposition on the engine surfaces of varnish, gum or sludge. Furthermore, many lubricating oil compositions which may be highly satisfactory for the lubrication of other mechanisms have been found wholly unsuitable for use as turbine oils.

The formation of varnishes, gums and sludges on engine surfaces is due at least in part to oxidation effects on mineral lubricating oils. In turbine oils the problem of oxidation is further aggravated, because in normal use turbine oils rapidly become contaminated with water.

It has heretofore been proposed to employ as oxidation inhibitors diamino diaryl alkanes, such as tetramethyland tetraethyldiamino diphenyl methane. However, the antioxidant potency of such compounds has not been entirely satisfactory because it is relatively low.

It is an object of this invention, therefore, to provide an addition agent for mineral oil lubricants which will inhibit the oxidative deterioration of such lubricants.

It is a further object of this invention to provide improved mineral oil lubricant compositions which are remarkably stable against oxidation under service conditions.

These and other objects are accomplished by the present invention wherein an addition agent for mineral oil lubricants is prepared by condensing N-diethylaniline, N-dimethylaniline and formaldehyde in the presence of an activated clay catalyst, and recovering the condensation product. The condensation product so obtained is a light-colored product which, when added to mineral oil lubricants, confers a remarkable stability against deterioration by oxidation. Such condensation products and the mineral oil lubricant compositions containing them are believed to be novel and are considered parts of our invention. Contrary to what may be exinvention, there are obtained light-colored condensation products which are non-resinous and which are readily soluble in mineral oils.

In performing the condensation, the reactants are mixed and heated to a maximum temperature of 350 F. We have found that if the temperature of 350 F. is exceeded to any substantial extent, the condensation product formed tends to be resinous and insoluble. In general, the preferred temperature for the condensation ranges from to 300 F.

The proportions of the reactants vary over a fairly wide range. For each mol of N-diethylaniline, N-dimethylaniline is employed in an amount of from 1 to 6 mole, and the amount of formaldehyde used is from 1 to 6 mols. Ordinarily, it is preferred to use from ,5 to 10 per cent by weight of the activated clay catalyst, based on the total weight of the reactants. However, smaller amounts, as low as 1 per cent by weight, and larger amounts, as high as 20 per cent by weight, may also be employed; but larger amounts than about 10 per cent by weight are ordinarily not necessary.

In lieu of formaldehyde, any ldehydeyielding compound, such as paraformaldehyde, dioxymethylene and trioxymethylene may be employed. In such case, the amount of formaldehyde-yielding compound used is based on the equivalent number of mols of formaldehyde yielded within the range of proportions of formaldehyde set forth hereinabove. Accordingly, as used in the appended claims, the term formaldehyde" is intended to include formaldehydeyielding compounds as well as formaldehyde itself.

Various activated clays may be employed in accordance with our invention. Such materials are well-known in the art and comprise a natural clay, such as bentonite, fullers earth, floridin and smectite, which has been acid treated in order to activate the clay. These materials are described in U. S. Patent 1,898,165, for example.

In preparing our new addition agents, the reactants and catalyst are placed into a reaction vessel which is then closed and the mixture heated with agitation under reflux until all of the formaldehyde or formaldehyde-yielding compound has been consumed. At this time, the water which is formed as a result of the condensation is removed, preferablyunder vacuum, and the dehydrated condensation product is then filtered to remove the activated clay catalyst. In some instances, it is desirable to d prepare our new addition agent in a, concentrate cordance with our invention are liquids or crystalline solids. While the exact nature of the chemical composition of the condensation products is unknown, all of the three reactants enter into a flnal unitary product. The exact manner in which the catalyst influences the reaction is unknown. volved, the use of an activated clay catalyst is an essential feature of our invention, since if the catalyst is omitted, black, insoluble, resinous condensation products are obtained.

The following examples illustrate the preparation of our new addition agent:

Example I.-Into a stainless steel vessel, there was introduced 1 pound mol of N-diethylaniline (149 pounds), 3 pound mols of N-dimethylaniline (363 pounds) and 3 pound mols of formaldehyde in a 37 per cent by weight aqueous solution (243 pounds). To this mixture, there was added 50 pounds of Filtrol (an activated montmorillonite catalyst). The vessel was closed and attached to a reflux condenser. The mixture was then heated to 210 F. and refluxed for 6 hours. The condensation product was then dried by distilling off all water, both that added with the formaldehyde and formed in the reaction, and heating to 280 F. The product was then filtered. It had the following properties:

Gravity, A. P. I. 11.7 Color, N. P, A. 5.5 Neutralization No. 2.1

Example II.-Example I was repeated using 1 mol of N-diethylaniline, 6 mols of N-dimethylaniline, 6 mols of formaldehyde and 10 per cent by weight of an activated clay. The filtered product had the following properties:

Gravity, A. P. I. 12.3 Color, N. P. A 4.5 Neutralization No. 1.8

Example III.--Another antioxidant was prepared under the conditions outlined in Example I using 1 mol of N-diethylaniline, 2 mols of N-dimethylaniline, 2 mols of formaldehyde and 10 per cent by weight of Filtrol (activated montmorillonite) The filtered product had the following properties:

Gravity, A. P. I. 10.6 Color, N. P. A 5.0

Neutralization No. 1.2

However, regardless of any theory in-' to the proportions desired in the final mineral oil lubricant composition. As stated, our new addition agents are remarkably eifective in inhibiting the oxidative deterioration of mineral oil lubricant compositions. For this purpose small amounts of our new addition agents are generally suflicient. For example, our addition agents may be added to mineral lubricating oils in minor amounts, say from 0.001 to 1 per cent by weight on the mineral oil, suiiiclent to inhibit the oxidative deterioration of the oil. Larger amounts of our new additionagents may be used if desired but it is ordinarily unnecessary to do so.

The following examples illustrate the remarkable antioxidant eifects of 'our new addition agents. In the following examples, the base oil and the same oil blended with our new addition agents are subjected to a standard oxidation test which measures the stability of the oils to oxida* tion. The oxidation test referred to is a standard test designated A. S. T. M. D943-47 T. Briefly, the test comprises subjecting the oil sample to oxygen at a temperature of C. (203 F.) in the presence of water and an iron-copper catalyst, and determining the time required to build up a neutralization number of 2. The flow of oxygen is maintained at 3 liters per hour. The remarkably effective stability to oxidation of mineral oil lubricant compositions containing our new addition agents is illustrated by the results shown in the following examples.

Example IV.An improved motor lubricating oil was prepared by treating a motor lubricating base stock with 0.5 per cent by weight of the antioxidant prepared according to Example I. A comparison of the properties of the base oil and the improved oil showed:

Base Improved Oil Oil Gravity, API Viscosity, SUV: Color, NPA Oxidation Test, ASTM D943-47T 203 F., 3 L.

Oxygen per HL:

Time Oxidized, Hrs Neutralization N o Example V.An improved steam turbine oil was prepared by treating a turbine oil base stock with 0.5 per cent by weight-oi an additive prepared according to Example I. A comparison of the properties of the base oil and improved tur-.

bine oil showed the following:

Base improved 0 1 Oil Gravity, API 28. 5 28. 4 Oxidation Test, ASTM D943-47'i 203 F., 3 L.

Oxygen per Hr.:

Time Oxidized, Hrs 180 3, 200 Neutralization No. 2. 0 2.0

application Serial No. 66,587, filed of even date herewith, we have described and claimed the condensation of mixtures of N-dimethylaniline and N-diethyltoluidines with formaldehyde in the presence of an activated clay to yield good antioxidants. Yet we have found that when xylidine, toluidine, or N-diethylanillne are individually condensed with formaldehyde in the presence of an activated clay, the resulting condensation products are not satisfactory antioxidants. It is obvious therefore, that the type of amine used to condense with the formaldehyde is critical and can only be determined by experiment. The instant application is based on the discovery that although N-diethylaniline when condensed alone with formaldehyde does not yield a satisfactory antioxidant, when mixtures of N-diethylaniline and N-dimethylaniline are condensed with formaldehyde in the presence of an activated clay, good antioxidants are obtained.

While we have shown in the examples the preparation of compounded lubricating oils, our invention is not limited thereto but comprises all mineral oil lubricant compositions containing our new addition agents, such as greases and the like.

If desired, other known addition agents may be incorporated. into the lubricant compositions prepared in accordance with our invention. For example, pour point depressants, extreme-pressure agents, viscosity index improvers and the like may be added.

Resort may be had to such modifications and variations as fall within the spirit of the invention and the scope of the appended claims.

We claim:

1. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of N-diethylaniline with from 1 to 6 mols of N-dimethylaniline, and 1 to 6 mols of formaldehyde in the presence of an activated clay catalyst at a temperature not in excess of 350 F. to condense together the three reactants, and recovering the condensation product.

2. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of N-diethylaniline with from 1 to 6 mols of N-dimethylaniline, and 1 to 6 mols of formaldehyde in the presence of an activated clay catalyst at a temperature of from 150 to 300 F.

to condense together the three reactants, and recovering the condensation product.

3. The process of preparing an addition agent for mineral oil lubricants which comprises adding 1 mol of N -diethylaniline with from 1 to 6 mols of N-dimethylaniline, l to 6 mols of formaldehyde and from 5 to 10 per cent by weight on the foregoing reactants of an activated clay catalyst to a mineral lubricating oil, heating the mixture at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering a solution of the condensation product in the mineral lubricating oil.

4. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of N-diethylaniline, 3 mols of N-dimethylaniline and 3 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature from to 300 F. to condense together the three react- I ants, and recovering the condensation product.

5. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of N-diethylaniline, 6 mols of N-dimethylaniline and 6 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

6. The process of preparing an addition agent for mineral oil lubricants which comprises heating 1 mol of N-diethylaniline, 2 mols of N-dimethylaniline and 2 mols of formaldehyde in the presence of 5 to 10 per cent by weight of an activated clay catalyst at a temperature of from 150 to 300 F. to condense together the three reactants, and recovering the condensation product.

7. A non-resinous condensation product of 1 mol of N-diethylaniline, 1 to 6 mols of N-dimethylaniline and 1 to 6 mols of formaldehyde, said product being obtained by the process of claim 1.

8. A non-resinous condensation product of 1 mol of N-diethylaniline, 3 mols of N-dimethylaniline and 3 mols of formaldehyde, said product being obtained by the process of claim 4.

9. A non-resinous condensation product of 1 mol of N-diethylaniline, 6 mols of N-dimethylaniline and 6 mols of formaldehyde, said product being obtained by the process of claim 5.

10. A non-resinous condensation product of 1 mol of N-dlethylaniline', 2 mols of N-dimethylaniline and 2 mols of formaldehyde, said product being obtained by the process of claim 6.

11. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sufficient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of 1 mol of N-diethylaniline, 1

to 6 mols of N-dimethylaniline and 1 to 6 mols formaldehyde, said product being obtained by the process of claim 1.

12. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, from 0.001 to 1.0 per cent by weight of said oil, of a, non-resinous condensation product of 1 mol of N-diethylaniline, 1 to 6 mols of N-dimethylaniline, and 1 to 6 mols of formaldehyde, said product being obtained by the process of claim 1.

13. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, suificient to inhibit the oxidative deterioration of said oil of a non-resinous condensation product of 1 mol of N-diethylaniline, 3 mols of N-dimethylaniline and 3 mols of formaldehyde, said product being obtained by the process of claim 4.

14. The lubricant composition of claim 13, wherein the condensation product is present in an amount of 0.5 per cent by weight.

15. A lubricant composition comprising a major amount of a mineral lubricating oil, and a minor amount, sumcient to inhibit the oxidative deterioration of said 011 of a non-resinous condensation product of 1 mol of N-diethylaniline, 6 mols of N-dimethylaniline and 6 mols of formaldehyde, said product being obtained by the process of claim 5.

16. The lubricant composition of claim 15,

7 wherein the condensation product is present in an amount of 0.5 per cent by weight.

17. A lubricant composition comprising a major amount oi a mineral lubricating oil, and

a. minor amount, suiiicient to inhibit the oxida: 5 tive deterioration 01' said 011 or a non-resinous 8 nnrmumcns crrm The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name v Date 1,584,473 Regal my 11, 1020 1,873,799 Vacher Aug. 23, 1932 1,954,484 Mattison Apr. 10, 1984 FOREIGN PA'I'ENTS Number Country, Date 12 ,021 Australia Rb. 29, 1928 256,394 Great Britain Aug. 12, 1928 284,958 Italy MEL-18, 1929 

1. THE PROCESS OF PREPARING AN ADDITION AGENT FOR MINERAL OIL LUBRICANTS WHICH COMPRISES HEATING 1 MOL OF N-DIETHYLANILINE WITH FROM 1 TO 6 MOLS OF N-DIMETHYLANILINE, AND 1 TO 6 MOLS OF FORMALDEHYDE IN THE PRESENCE OF AN ACTIVATED CLAY CATALYST AT A TEMPERATURE NOT IN EXCESS OF 350*F. TO CONDENSE TOGETHER THE THREE REACTANTS, AND RECOVERING THE CONDENSATION PRODUCT. 